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3.04 Functions and
disorders of the eye
3.04 Understand the functions and
disorders of the sensory system 1
3.04 Understand the functions and
disorders of the sensory system
3.04 Understand the functions and
disorders of the sensory system 2
Essential Questions
• What are the functions of the sensory system?
• What are some disorders of the sensory system?
• How are sensory system disorders treated?
• How do you relate the body’s communication to
the sensory system?
Understanding the
functions of the eye
3.04 Understand the functions and
disorders of the sensory system 3
Understanding the
functions of the eye External eye Orbit- The cavity that houses the
eye
Eyelids and eyelashes
Women blink twice as often as men. Why do we blink? To prevent particles from entering the eye.
Conjunctiva- Protects the
exposed eye surface
Lacrimal apparatus-
Produces and stores tears
Extrinsic muscles- Muscles
responsible for moving the eye
3.04 Understand the functions and
disorders of the sensory system 4
Understanding the
functions of the eye External eye Extrinsic
muscles- Move the
eye within the orbital
socket and are
attached to the
outside of the sclera
3.04 Understand the functions and
disorders of the sensory system 5
Understanding the
functions of the eye
Internal eye
Cornea- allows
passage of light rays.
Iris- controls the size
of the pupil when light
passes into the eye
Pupil- Allows light
to pass into the eye
3.04 Understand the functions and
disorders of the sensory system 6
Understanding the
functions of the eye
Internal eye
Ciliary body- muscles
that alter the shape of the
lens which allows focusing
Lens-Thins and thickens
to allow light to focus on
the retinal surface
Aqueous humor-
bathes the iris, pupil and
lens with fluid
3.04 Understand the functions and
disorders of the sensory system 7
Understanding the
functions of the eye
Internal eye
Sclera- maintains
the shape of the eye; bends outside light rays to focus on the retina
Choroid- Contains
blood vessels and pigment that prevent internal reflection of light rays
Retina- contains
nerve endings that receive and interpret the rays of light for vision
3.04 Understand the functions and
disorders of the sensory system 8
Understanding the
functions of the eye
Internal eye
Vitreous
humor -maintains eye shape;
refracts light rays
3.04 Understand the functions and
disorders of the sensory system 9
Understanding the
functions of the eye
3.04 Understand the functions and
disorders of the sensory system 10
Macula: The
yellow disc in
the back of the
eye
Understanding the
functions of the eye
Process of Seeing
Trace the field of vision. Images in the
light> cornea > pupil > lens > light rays are bent or refracted > retina > rods and cones pick up the stimulus > optic nerve > optic tracts > occipital lobe of the brain to interpretation
3.04 Understand the functions and
disorders of the sensory system 11
Why can’t you see in the dark?
Understanding the
functions of the eye
3.04 Understand the functions and
disorders of the sensory system 12
What happens as you move
your paper away from and
toward to your eye?
Vision
Rods and cones of the retina
What are the functions of the rods and cones?
3.04 Understand the functions and
disorders of the sensory system 13
Understanding the
functions of the eye
3.04 Understand the functions and
disorders of the sensory system 14
3.04 Understand the functions and
disorders of the sensory system 15
Vision Activity
Do you see what I see?
Disorders of the eye
3.04 Understand the functions and
disorders of the sensory system 16
Cataract
Glaucoma
Diabetic retinopathy
Have you heard of these conditions?
What do you know about them?
Disorders of the eye
Describe this lens. The lens gradually becomes
cloudy. It occurs frequently
in people over 70. Vision
becomes blurred, pupil
becomes milky white.
3.04 Understand the functions and
disorders of the sensory system 17
Cataract
Disorders of the eye
Cataract
How is a
cataract
treated? Surgical removal of the
lens and lens implant.
3.04 Understand the functions and
disorders of the sensory system 18
Disorders of the eye
Color blindness
Do you see the number?
What is color blindness? Disorder of the retina that causes
an inability to distinguish
between red and green colors.
What causes it? It is
inherited due to genes on the X
chromosome
3.04 Understand the functions and
disorders of the sensory system 19
Disorders of the eye
Conjunctivitis
What is conjunctivitis? Inflammation of the membrane that lines the
eye
What are the symptoms? Red
swollen eyes
What causes it? Viruses or bacteria
How is it treated? Eye washes or eye
irrigations to cleans the conjunctiva
3.04 Understand the functions and
disorders of the sensory system 20
Detached retina
3.04 Understand the functions and
disorders of the sensory system 21
What is it? When the retina
becomes detached from the
choroid layer
What is the relevance to
health? This can happen as a
result of a traumatic accident.
However, with aging, it may
happen as the vitreous fluid
contracts and pulls on the retina
causing it to tear.
3.04 Understand the functions and
disorders of the sensory system 22
Detached retina
Compare this process
to the previous picture.
Disorders of the eye Diabetic retinopathy Cause: Changes in the blood
vessels in the retina. Blood vessels may swell and leak or abnormal blood vessels may grow on the retina.
What are the symptoms? None in the early stages, but as it advances, people can see red spots if bleeding occurs.
Prognosis: Blindness if untreated.
3.04 Understand the functions and
disorders of the sensory system 23
Disorders of the eye
Glaucoma
Description: Overproduction
of aqueous humor or obstruction of
its outflow causing excessive
pressure and results in destruction
and atrophy of the optic nerve
Symptoms: gradual aching
feeling, loss of peripheral vision
and a halo around light.
How is it diagnosed? Tonometry, opthalmoscope to
visualize the optic nerve.
How is it treated?
Medicated eye drops that increase
the outflow of aqueous fluid
3.04 Understand the functions and
disorders of the sensory system 24
Tonometry
Disorders of the eye
Macular degeneration
What is macular degeneration? Occurs
with aging. It is a reduction or loss of central
vision.
Two types
Atrophic (Dry)
Exudative (Wet)
Symptoms: Dimming or distortion of vision
especially when reading
What is the treatment? None for dry type;
laser treatment for wet type.
3.04 Understand the functions and
disorders of the sensory system 25
3.04 Understand the functions and
disorders of the sensory system 26
Presbyopia: The lens loses its elasticity making it
difficult to focus on close objects.
•Usually occurs after age 40
•Correction with glasses
An irregular curvature of the cornea or lens which causes
blurred vision and eyestrain
•Special prescription glasses help this condition
3.04 Understand the functions and
disorders of the sensory system 27
Hyperopia (farsightedness): Objects must be moved
farther away from the eye to be seen clearly.
•Convex lenses help correct this situation
Myopia (nearsightedness) Objects must be
moved closer to the eye to be seen clearly
•Concave lenses correct this situation
Testing vision
How do we test visual
acuity?
3.04 Understand the functions and
disorders of the sensory system 28
3.04 Understand the functions and
disorders of the sensory system
3.04 Understand the functions and
disorders of the sensory system 29
Essential Questions
• What are the functions of the sensory system?
• What are some disorders of the sensory system?
• How are sensory system disorders treated?
• How do you relate the body’s communication to
the sensory system?
3.04 Functions and
disorders of the eye
The End
3.04 Understand the functions and
disorders of the sensory system 30